The disclosures herein relate generally to information handling systems and more particularly to an information handling system employing a battery discharge system that accommodates multiple batteries.
As the value and use of information continue to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for is business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Portable information handling systems often include battery systems to provide power during standalone portable operation and in the event of system power failure when docked to the AC mains by a docking station. A high capacity secondary battery is often used in addition to a primary battery to supply power to the system. These batteries are coupled via a discharge circuit to the main power input or power rail of the system. The discharge circuit controls which particular battery is providing power to system. It is desirable that the discharge circuit be able to rapidly switch between the batteries without causing a system shutdown.
Prior battery discharge circuits were able to discharge the primary and secondary batteries by imposing constraints on the cell stack. The cell stacks which formed both the primary and secondary batteries were forced to be the same. In other words, if the primary battery employed four 3.6 volt lithium ion cells, then the secondary battery also was required to employ the same cell stack, namely four 3.6 volt lithium ion cells. Using the same cell stack assured the same working range of voltage for both the primary and secondary battery. With this constraint in force, a discharge circuit employing a respective diode to connect each battery “diode OR” to the systems' power rail could be employed. Whichever battery had the higher voltage at a particular point in time would forward bias its respective diode and couple the battery to the power rail. Unfortunately, this approach has a number of shortcomings. First, it is inefficient due to diode losses. Second, such a discharge circuit provides no control over which battery discharges first because the battery with the highest voltage will be the battery which is connected to the power rail. In other words, in the above approach the discharge circuit can not discharge one battery independent of the other battery.
Another conventional discharge battery discharge circuit employed so-called smart batteries and a smart battery selector compliant with the Smart Battery Specification (SBS) to control the battery discharge sequence. Unfortunately, that approach relies on relatively expensive SBS compliant integrated circuits and expensive smart batteries. This approach does not function with less expensive so-called dumb batteries.
What is needed is an information handling system with a discharge circuit that can discharge each battery independently. It is further desirable that the discharge circuit be independent of battery cell stack, state of charge and battery chemistry. It is also very desirable that the discharge circuit have minimal losses to more effectively operate in a portable information handling system environment.